Hanging on the wall in my office is a painting by Francis Bicknell Carpenter — “First Reading of the Emancipation Proclamation of President Lincoln.” The 1864 painting depicts Abraham Lincoln sitting in his office with members of his cabinet. It is a stark reminder today of “the better angels of our nature.”

Those men with Lincoln — Edwin M. Stanton, Secretary of War; Salmon P. Chase, Secretary of the Treasury; Gideon Wells, Secretary of the Navy; Caleb B. Smith, Secretary of the Interior; William H. Seward, Secretary of State; Montgomery Blair, Postmaster General and Edward Bates, Attorney General — were, as Doris Kearns Goodwin proclaimed, a “Team of Rivals.”

The Emancipation Proclamation was an executive order issued by Abraham Lincoln in the fall of 1862 that took effect on Jan. 1, 1863. In the wake of the unrest in Charlottesville, Virginia, it is important to remember what Lincoln did over 150 years ago.

Some say as a draft of the Emancipation Proclamation sat in his desk, Lincoln wrote a letter to Horace Greeley the editor of the New York Tribune, “My paramount object in this struggle is to save the Union ... If I could save the Union without freeing any slave I would do it, and if I could save it by freeing all the slaves I would do it; and if I could save it by freeing some and leaving others alone I would also do that.”

Initially, Lincoln’s advisors were not in support of the Emancipation Proclamation. When Lincoln first proposed the idea many of his cabinet secretaries were concerned that the Proclamation was too radical.

During the meeting depicted in Carpenter’s painting, Secretary of War Stanton, brought up the idea of arming the freed slaves. Lincoln was thinking of something bigger. He rose, turned to his Cabinet and told them that he had prepared a draft of a proclamation that would free all of the slaves in the Confederate States.

Stanton and Bates supported Lincoln’s idea. Seward and Chase were reluctant and Blair was opposed. Welles and Smith apparently remained silent.

Seward suggested waiting for a Union victory to legitimize the Union’s authority to issue such a far-reaching order. The Battle of Antietam was the “victory” Lincoln was looking for. He issued the Proclamation just five days after the battle.

Chase wrote a letter to Carpenter in 1866, an apparent effort to revise history, noting that he and Stanton appear symbolically on Lincoln’s right in the painting, having "thoroughly endorsed and heartily welcomed the measure," and the cabinet members who had at first "doubted, or advised delay, or even opposed" the proclamation appear on Lincoln’s left.

The Emancipation Proclamation freed the slaves in the 10 Confederate States still fighting the Civil War. Interestingly, the Proclamation did not outlaw slavery or free the slaves in the Union states that still permitted it.

The proclamation also authorized the enlistment of freed slaves in the Union Army, increasing the Union's available manpower.

Maybe most important for the war effort, the Proclamation also prevented European forces from intervening in the war on behalf of the Confederacy. The proclamation made the abolition of slavery a goal of the war. Most European countries had abolished slavery and were squeamish about slavery in the Confederacy.

As Lincoln hoped, the Proclamation swung foreign popular opinion in favor of the Union and ultimately achieved his goal at saving the Union.

President Lincoln anticipated that the Emancipation Proclamation would be the most important aspect of his legacy. “I never, in my life, felt more certain that I was doing right, than I do in signing this paper,” he declared. “If my name ever goes into history it will be for this act, and my whole soul is in it."

— Matthew T. Mangino is of counsel with Luxenberg, Garbett, Kelly & George P.C. His book “The Executioner’s Toll, 2010” was released by McFarland Publishing. You can reach him at www.mattmangino.com and follow him on Twitter at @MatthewTMangino.